Matthew is 3 times as old as Jenny. In 7 years, he will be twice as old as she will be then. How old is she now?

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baxthum8's profile pic

baxthum8 | High School Teacher | (Level 3) Associate Educator

Posted on

Now: Let Jenny be "x", then Matthew is "3x".

In 7 years, Matthew will be 3x + 7, and Jenny is x + 7.

Matthew is twice as old as Jenny, therefore

`3x + 7 = 2(x + 7)`

`3x + 7 = 2x + 14`

`x + 7 = 14`

`x = 7`

Jenny is 7 years old now.

Check:

Now:  Jenny is 7, which makes Matthew 21, 3 times as old.

In 7 years, Jenny will be 14 and Matthew will be 28, which is twice as old.

tonys538's profile pic

tonys538 | Student, Undergraduate | (Level 1) Valedictorian

Posted on

Matthew is 3 times as old as Jenny. In 7 years, he will be twice as old as she will be then.

If Matthew is x years old now, Jenny's age is equal to x/3.

In 7 years, Matthew's age will be x + 7 and Jenny's age will be x/3 + 7

As Matthew would be twice as old as Jenny we get the equation:

x + 7 = 2*(x/3 + 7)

x + 7 = 2x/3 + 14

x/3 = 7

x = 21

Matthew's present age is 21 and Jenny is 7 years old now.

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